Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands			1 Months Ended	2 Months Ended	12 Months Ended
	Feb. 19, 2016	Jan. 01, 2016	Jul. 31, 2014	Feb. 25, 2016	Dec. 31, 2015	Dec. 31, 2014
Subsequent event
Dividend declared (in dollars per share)			$ 0.06			$ 0.04
Stock Repurchased During Period, Shares					10,600	10,375
Payments for Repurchase of Common Stock					$ 99,598	$ 250,037
Subsequent Event
Subsequent event
Dividend declared (in dollars per share)	$ 0.06
Stock Repurchased During Period, Shares		300
Payments for Repurchase of Common Stock		$ 1,700
Stock Repurchase Program, Remaining Authorized Repurchase Amount		298,700
Stock Repurchase Program, Authorized Amount		$ 400,000
Subsequent Event | Senior Notes
Subsequent event
Debt Instrument, Repurchased Face Amount				$ 120,100
Cash outflow to repurchase senior notes				$ 117,100